With the advent of deep winter season, the temperature in the north gradually declines, and the tomato cultivated in wintering greenhouses faces a low temperature test. Tomato is a thermophilic crop and its tolerance in cold environments is limited. When the tomato or nursery is cultivated in winter and spring or deep winter season, it will suffer low temperature and chilling when it encounters low temperature or frost. When the temperature of deep winter greenhouse is 5°C～10°C for a long time, the leaves will appear dark green or flooded. When the temperature continues to linger at 5°C, the leaves will lose their green edges. In the sudden encounter of large temperature changes in frost (temperature below 2 °C), anthocyanin increased the leaves to show purple and wilting to death. In the low-temperature environment where the temperature is below 5°C for a long time, the plants will lose their green due to cold damage and become white-like, and the plants will die due to chilling injury.
This symptom is very easy to confuse with the symptoms of magnesium deficiency in tomato. Magnesium deficiency is caused by the lack of magnesium causing chlorosis and chlorosis of the mesophyll. Although due to the low temperature and excessive N and P fertilizers, it will affect the absorption of magnesium fertilizer and cause magnesium deficiency disease easily. However, in analyzing the seasonal climate, if there is chlorosis of the leaf in the cold winter, the first thing to consider is the low-temperature freezing injury. When the tomato lives in a low temperature environment below 5°C for a long time, the plants will be chlorogenic by the chilling leaves and appear bleached. In severe cases, the whole plant will die due to chilling injury. Starting from the seasonal climate, checking its management level and insulation measures, it will distinguish the difference between freezing injury and deficiency. Attention to timely symptomatic treatment can minimize unnecessary losses.
Freezing damage remediation: In addition to selection of cold-resistant, low-temperature, low-light varieties, the management of greenhouse tomato from the insulation to start, improve the greenhouse insulation measures are the main measures for the treatment of freezing injury. Thicken the thickness of the earth wall, increase the density of weeds, and deduct arch sheds in greenhouses to increase temperature and resist cold. Suddenly encounter frost and cold, temporary heating measures should be taken to burn the coal stove or shop floor hotline. Chemical control can use cold-resistant agent, can be used 3.4% Bi protect wettable powder 5000 ~ 7500 times, or 15 liters of water plus 50 grams of brown sugar plus 0.3% potassium dihydrogen phosphate spraying.
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